The present invention relates to an electrophotographic photoconductor used in electrophotographic apparatuses, such as printers and copying machines. More specifically, the present invention relates to a charge generation material for the electrophotographic photoconductor and a method of manufacturing a electrophotographic photoconductor which includes the charge generation material.
Referring now to FIG. 1(a), a conventional function-separation-type electrophotographic photoconductor includes a conductive substrate 1, an undercoating layer 2, and a photoconductive layer 5. Photoconductive layer 5 contains a charge generation material that generates charges in response to exposure light. In a conventional function-separation-type electrophotographic photoconductor, photoconductive layer 5 includes a charge generation layer 3 for generating charges and a separate charge transport layer 4 for transporting the charges. Referring now to FIG. 1(b), a conventional monolayer-type electrophotographic photoconductor includes conductive substrate 1, undercoating layer 2, and photoconductive layer 5 which embodies charge generation and charge transport functions. Undercoating layer 2 is not a required element of either type of conventional photoconductor.
Metal phthalocyanines which contain a tetravalent metal ion to which an oxygen ion is bonded have been investigated intensively for the use as a charge generation material in electrophotographic photoconductors. Such metal phthalocyanines are also known to be stable in water. Titanyloxyphthalocyanine is an example of the above-described metal phthalocyanines.
The structural formula of titanyloxyphthalocyanine is shown in FIG. 2. A method of chemical synthesis of titanyloxyphthalocyanine is described by F. H. Moser, et. al. in "The Phthalocyanines", CRC Press (1983), the entirety of which is herein incorporated by reference. Photoconductive materials and electrophotographic photoconductors which employ titanyloxyphthalocyanine, and manufacturing methods for these are disclosed in the following publications: Japanese Unexamined Laid Open Patent Applications S59-49544, S59-166959, S59-204045, S61-109056, S61-171771, S62-61054, S62-67094, S63-116158, S63-218768, S64-17066, H01-120564, H01-138562, H01-299874, H02-8256, H02-28265, H05-320167, H06-289628, and U.S. Pat. No. 4,664,997.
Japanese Unexamined Laid Open Patent Application No. H06-289628 discloses the manufacture of an electrophotographic photoconductor which employs titanyloxyphthalocyanine as a charge generation material. The method of manufacture of the photoconductor employs a dispersion liquid, prepared by dispersing titanyloxyphthalocyanine in a dispersion medium which contains water at an amount (by weight) equal to or greater than the amount of the titanyloxyphthalocyanine. Although Japanese Unexamined Laid Open Patent Application No. H06-289628 discloses that the crystal form of titanyloxyphthalocyanine is maintained by adding water to the dispersion medium in the dispersion process, no description of the water contained in the titanyloxyphthalocyanine crystal or the titanyloxyphthalocyanine molecular aggregate is found.
Many proposals have been presented regarding photoconductive materials containing titanyloxyphthalocyanine. However, the relationship between the titanyloxyphthalocyanine molecular aggregate and water in the manufacturing processes for electrophotographic photoconductors that use photoconductive material containing titanyloxyphthalocyanine has not been clarified. As a result, satisfactory electrophotographic properties have not been obtained in conventional photoconductors that contain titanyloxyphthalocyanine. In addition, coating liquids that contain titanyloxyphthalocyanine have unsatisfactorily short pot lives.